1. Field of the Invention
The present invention relates to communication in which an electronic certificate is used, particularly to a communication apparatus that mediates communication using the electronic certificate, a communication method, a communication program, and a communication system.
2. Description of the Related Art
Conventionally, various techniques of communicating with an inside device from the outside through a network such as the Internet are studied in order to remotely maintain an inside server. In the communication, there is a need for a countermeasure that prevents leakage or tampering of information used in the communication or information accumulated in the device. The communication in which an electronic certificate is used can be cited as an example of the countermeasure.
Japanese Laid-Open Patent Publication No. 2001-249899 discloses a technique in which an upper-level instrument having interface means to an external network is placed in a local network belonging to a control target instrument. In the technique, the upper-level instrument transmits information authenticating the control target instrument to a service center on the external network. When the service center authenticates the control target instrument, the service center and the control target instrument directly conduct encrypted communication.
Press Release “Ricoh globally develops remote management service “@Remote” supporting operational management about two million digital multi-function peripherals/printers worldwide in 2007”, Dec. 12, 2004, http://www.ricoh.co.jp/release/by_field/other/2004/1210.html discloses a technique in which the inside server mediates communication between the inside control target instrument and a technical call center that collects information for maintenance of the control target instrument. In the technique, the inside server communicates with control target instrument through a LAN (Local Area Network), thereby conducting the encrypted communication with the outside technical call center using the electronic certificate.
In the technique disclosed in Japanese Laid-Open Patent Publication No. 2001-249899, when the communication between the control target instrument and the service center is realized by key cryptography using the electronic certificate, it is necessary for the control target instrument to include information-processing ability to communicate using the electronic certificate. Accordingly, due to a so-called low-specification control target instrument, when the processing ability necessary for encode (encryption) and decode (decryption) for the communication in which the electronic certificate is used runs short, or when the ability to authenticate the certificate of the other end runs short, the technique cannot be applied.
On the other hand, in the technique disclosed in Press Release, it is not necessary for the control target instrument to communicate in which the electronic certificate is used. Accordingly, the technique can be applied when the inside server has the processing ability even if the control target instrument does not have the processing ability.
However, in the technique, when communicating with the technical call center, the inside server uses the electronic certificate of the inside server, but not the electronic certificate of the control target instrument that becomes the target of data collection performed by the technical call center. Therefore, the technical call center cannot confirm validity of the control target instrument that is of the target of the maintenance during the maintenance of the control target instrument.